Study On Seismic Behavior Of Non-Ductile RC Square Columns Strengthened With Large Rupture Strain FRP Under High Axial Compression Ratio

In recent years,earthquake disasters occur frequently at home and abroad.Some reinforced concrete bridge piers are prone to partial or integral destruction and collapse under the action of earthquake,which damages the life and property safety of the country and people.These reinforced concrete structures were designed and constructed according to the old code,and only the vertical load was considered without seismic design.There are some problems such as insufficient stirrup ratio and poor ductility,and their seismic performance cannot reach the seismic standard of the latest design code,so it is urgent to carry out seismic reinforcement.This kind of structure is defined as the non-ductile reinforced concrete structure,which is studied in this thesis.Recently fiber reinforced polymer(FRP)has been widely used in the field of RC structural reinforcement due to its advantages of good corrosion resistance,light weight,high strength,good fatigue resistance and convenient construction.The FRP reinforcement method is widely used in the seismic reinforcement of reinforced concrete structures because of its characteristics of simple construction,fast and efficient construction,almost no additional load and no influence on the structure appearance.The traditional FRP materials has the characteristics of high elastic modulus and low fracture strain.A new type of large rupture strain FRP(LRS FRP)with larger fracture Strain(more than 5%)may improve the ductility and seismic performance of structures in seismic reinforcement.Based on this background,the seismic performance of LRS FRP reinforced non-ductile reinforced concrete square columns is studied in this thesis.The main research contents are as follows:(1)Pseudo-static tests were carried out on 10 non-ductile RC square columns strengthened with LRS FRP,including 1 contrast column,3 columns strengthened with PET FRP,3 columns strengthened with PET FRP strips and 3 columns strengthened with PEN FRP.The effects of FRP types,reinforcement types and reinforcement layers on the failure modes and seismic performance of FRP confined columns were studied by analyzing the failure modes,seismic performance parameters and strains of steel bars and FRP.(2)Based on the stress-strain design model of large-strain FRP-confined concrete and the fr P-confined reinforcement buckling model,the finite element analysis of the test results was carried out on the Open Sees platform,and the simulation was compared with the test results.The stress and strain development of concrete and steel bar in plastic hinge zone is analyzed in depth and verified with theoretical models.On this basis,the effects of FRP reinforcement thickness,axial compression ratio and longitudinal reinforcement ratio on the seismic performance of LRS FRP reinforced rc columns are studied.